Organic electro-luminescent device, manufacturing method for the same, and electronic equipment

ABSTRACT

The presentation provides a manufacturing method for forming an organic electro-luminescent device by forming a homogeneous light emitting layer which does not incur phase separation. The light emitting layer is formed by discharging ink compositions formed of at least two electro-luminescent materials on the substrate following the order which starts with an ink composition which has the fewest number of organic electro-luminescent materials or which is most difficult to be phase separated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electro-luminescent deviceprovided with electric light emitting elements used for displays, anddisplay light sources, and the like, a manufacturing method for thesame, and electronic equipment.

2. Description of the Related Art

The development of light emitting elements using organic materials forspontaneous light emitting-type displays in place of liquid crystaldisplays has recently been proceeding at a rapid pace. With respect toan organic electro-luminescent device equipped with a light emittingcomponent using an organic material in the light emitting layer, arelated art method for forming a low molecular weight layer using anevaporation process is disclosed from page 913 in Appl. Phys. Lett. 51(12), 21 Sep. 1987, and a related art method for coating a largemolecular weight layer is disclosed from page 34 of Appl. Phys. Lett. 71(1), July 1997.

In the case of using a low molecular weight material for coloring, alight emitting material differing from that of mask lifting is vapordeposited and formed onto the desired image. On the other hand, in thecase of a large molecular weight material, much attention is beingplaced on performing the coloring using an ink jet method, due torefinement and ease with which the patterning can be accomplished. Thefollowing examples are related art methods for forming an organicelectro-luminescent component by such an ink jet method: Japanese PatentApplication, First Publication No. Hei 7-235378, Japanese PatentApplication, First Publication No. Hei 10-12377, Japanese PatentApplication, First Publication No. Hei 10-153967, Japanese PatentApplication, First Publication No. Hei 11-40358, Japanese PatentApplication, First Publication No. Hei 11-54270, and Japanese PatentApplication, First Publication No. Hei 11-339957.

In addition, from the standpoint of component manufacturing, in order toenhance the light emitting efficiency and durability, the formation of ahole injection/transport layer between the electrode and light emittinglayer is widely performed as disclosed from page 913 in Appl. Phys.Lett. 51 (12), 21 Sep. 1987. Formation of a layer has been performed bya coating process, such as spin coating or the like, using a conductivemacromolecule as the buffer layer and/or hole injection/transport layer,e.g., a polythiophene derivative and/or polyaniline derivative (Nature,357, 477, 1992). With respect to a low molecular weight material,formation of a layer using a phenylamine derivative, as the holeinjection/transport layer, by evaporation has been reported.

The aforementioned ink jet methods are extremely effective for simplyforming a layer having a refined pattern without wasting the lightemitting layer material including the organic electro-luminescentmaterial.

When forming a light emitting layer using an organic electro-luminescentmaterial according to an ink jet method, a composition is employed whichincludes a solute and solvent, wherein the aforementioned soluteincludes an organic electro-luminescent material.

As the aforementioned composition, it is possible to use a compositionincluding only one type of organic electro-luminescent material.However, compositions including a plurality of organicelectro-luminescent materials are more widely used. For example, bymixing a light emitting material and a fluorescent material, it ispossible to change the light illuminated from the aforementioned lightemitting material to a light having a different wavelength due to thepresence of the aforementioned fluorescent material.

In this manner, in the case of a plurality of organicelectro-luminescent materials, in order to obtain the desired lightcharacteristics, it is necessary to form a layer in a state in whicheach of the aforementioned organic electro-luminescent materials isuniformly mixed without separation therefrom.

However, the droplets used in the formation of a thin layer according tothe ink jet method are extremely small, and the evaporation time isshort. As a result, the solvent molecules that are evaporated from thedroplets are saturated prior to being sufficiently dispersed from thesubstrate area, such that even the resultant thin layer is re-dissolved.Furthermore, at the time of re-dissolving the aforementioned, therespective organic electro-luminescent materials phase separate fromeach other, which in turn results in problems, such as degradation ofthe performance characteristics of the organic electro-luminescentdevice.

SUMMARY OF THE INVENTION

The present invention addresses the above-described problems. An objectof the present invention is to provide a manufacturing method, capableof forming a homogeneous luminescent layer which causes no phaseseparation during formation by the ink-jet method, and which is alsocapable of providing organic electro luminescence devices havingsuperior display properties. In addition to the manufacturing method, anobject of the present invention is to provide organicelectro-luminescence devices having homogeneous luminescent layers andalso having superior display properties. An object of the presentinvention is also to provide electronic equipment provided with thepresent organic electro-luminescent devices.

A first aspect of the present invention provides a manufacturing methodfor an organic electro-luminescent device including the steps of forminglight emitting layers by discharging above a substrate at least twocompositions, each including at least one organic electro-luminescentmaterial, the order of discharging the compositions above the substratestarting with a composition which has the fewest number of organicelectro-luminescent materials.

It was observed that problems of the phase separation occur more easilywith compositions including a larger number of organicelectro-luminescent materials, and thus in the discharge formation of alayer, those compositions including a larger number of organicelectro-luminescent materials are processed after the compositionscomprising a fewer number of organic electro-luminescent materials. As aresult, the aforementioned phase separation due to re-dissolutionfollowing completion of the discharge formation of the film can beprevented, and an organic electro-luminescence device possessingsuperior display properties can be reliably manufactured.

According to a second aspect of the present invention, a manufacturingmethod for an organic electro-luminescent device is provided thatincludes the steps of forming light emitting layers by discharging,above a substrate, at least two compositions, each including at leastone organic electro-luminescent material. When discharging compositionswhich have the same number of organic electro-luminescent materials, theorder of discharging said compositions above the substrate starting witha composition which is most difficult to be phase separated after thelayer is formed.

According to the present invention, the organic electro-luminescentcomposition, which is liable to be phase separated after the filmformation, is discharge formed after the discharge formation of theother organic electro-luminescent composition, which is difficult to bephase separated. Thus, it becomes possible to thereby prevent the phaseseparation due to re-dissolution after the discharge formation, whichresults in making it possible to provide a manufacturing method oforganic electro-luminescent devices having superior display properties.

A third aspect of the present invention provides a manufacturing methodfor the organic electro-luminescent device, such that during twocontinuous cycles of discharging said compositions, the subsequentdischarge of a composition is preferably performed after the droplets ofthe composition discharged in a first cycle are dried.

According to a fourth aspect of the present invention, the manufacturingmethod for an organic electro-luminescent device includes the steps offorming the light emitting layer after forming steps of a plurality offirst electrodes corresponding to a plurality of pixel regions, a banklayer that partitions the plurality of pixel regions, and a holeinjection/transport layer on said plurality of first electrodes on saidfirstelectrode. The forming process further includes the step of forminga second electrode on the light emitting layer.

Providing banks makes it possible to perform the discharge formation ofa layer by completely separating the two or more ink compositions intoseparate pixel regions. As a result, it is possible to easily maintainthe independence of each light emitting layer, and thereby obtain anorganic electro-luminescent device having superior display properties.In addition, a hole injection/transport layer is provided so as toachieve both a high luminescent efficiency and enhanced durability.

Furthermore, the counter electrode includes a cathode in the case whenthe image electrode is anode, and includes an anode electrode in thecase when the image electrode is cathode.

The organic electro-luminescent device of the present invention isobtained by using an aforementioned method for manufacturing an organicelectro-luminescent device according to the present invention. It ispossible to obtain an organic electro-luminescent device having auniform light emitting layer and superior display properties.

The present invention also provides an electronic equipment providedwith an organic electro-luminescent device produced by the abovemanufacturing process.

According to the present invention, it is possible to provide electronicequipment that is equipped with a display apparatus having superiordisplay properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 2 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 3 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 4 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 5 is a cross-section view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 6 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 7 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIG. 8 is a cross-sectional view showing a process of a manufacturingmethod for manufacturing an organic electro-luminescent device accordingto an embodiment of the present invention;

FIGS. 9A and 9B are graphs showing light emitting spectra of a greenlight emitting layer according to an example and comparative example ofthe present invention; wherein FIG. 9A is a graph that shows the lightemitting spectrum of a comparative example of the invention; and FIG. 9Bis a graph that shows the light emitting spectrum of an example of theinvention.

FIGS. 10A, 10B and 10C are perspective views showing electronicequipment equipped with an organic electro-luminescent devicemanufactured according to a manufacturing method of the presentinvention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following, a manufacturing method for manufacturing an organicelectro-luminescent device according to the present invention will bedescribed with reference to FIGS. 1-7.

The manufacturing method according to the present embodiment includes abank formation process; a plasma treatment process; a holeinjection/transport layer formation process; a surface reformingprocess; a light emitting layer formation process; a cathode formationprocess; and a sealing process.

As shown in FIG. 1, according to the aforementioned bank formationprocess, bank layers 12 separating each pixel region are formed bysequentially layering an inorganic substance bank layer 12 a and organicsubstance bank layer 12 b on a transparent electrode 11 including ITO orthe like, which is formed on a substrate 10 onto which TFT or the like(not shown in the Figures) has been pre-provided when necessary.

The aforementioned inorganic substance bank layer 12 a may be formed byforming an inorganic layer of SiO₂, TiO₂, SiN, and the like on theentire surface of the substrate 10 and transparent electrode 11according to, for example, a CVD process, a spattering process, anevaporation process, or the like; patterning the aforementionedinorganic layer using etching or the like; and then providing an opening13 a in the aforementioned transparent electrode 11. However, at thistime, the inorganic substance bank layer 12 a extends to the marginalareas of the transparent electrode 11.

The layer thickness of the aforementioned inorganic substance bank layer12 a is preferably in the range of 50-200 nm, with a value of 150 nmbeing particularly preferred.

Subsequently, an organic substance bank layer 12 b is formed on theentire surface of the substrate 10, transparent electrode 11, andinorganic substance bank layer 12 a.

In addition, the organic substance bank layer 12 b is formed by firstdissolving a standard resist, e.g., acrylic resin, polyamide resin, orthe like, in a solvent, and then coating this solution by spin coating,dip coating, or the like.

The organic substance bank layer 12 b is then etched by aphotolithography technique or the like to provide an opening 13 b. Thisopening 13 b of the aforementioned organic substance bank layer 12 b ispreferably formed to be slightly larger than the opening 13 a of theinorganic substance bank layer 12 a. In this manner, an opening 13 whichopens through both the inorganic substance bank layer 12 a and organicsubstance bank layer 12 b is formed above the transparent electrode 11.

Furthermore, the plane shape of this opening 13 is not particularlyimportant and may include a circle, oval, square, or stripe. However, inthe case of a square or the like, due to the surface tension of the inkcomposition, it is preferable to round out the corners thereof.

Subsequently, in the plasma treatment process, a region of ink affinityand an ink repellent region are formed on the surface of the bank member12.

This plasma treatment process is divided into a pre-heating process, anink affinity process that imparts ink-affinity to the entire surface, anink repellent process that makes the organic substance bank layer 12 bink repellent, and a cooling process.

In the pre-heating process, the substrate 10 including the bank member12 is heated to a predetermined temperature. This heating is performedby installing a heater, for example, at a stage in which the substrate10 is loaded within the plasma treatment chamber, and heating thesubstrate 10 to 70 to 80° C., for example, using this heater at thedesired stage.

By performing this pre-heating process, even in the case when the plasmatreatment is conducted continuously on a plurality of substrates, it ispossible to achieve almost constant plasma treatment conditions fromimmediately after commencing the treatment to immediately prior toterminating the treatment. As a result, it is possible to impart auniform affinity with respect to the composition ink of the bankportions 12 between substrates 10, which in turn allows for themanufacture of a display apparatus having a constant product quality.

In addition, the substrate 10 is pre-heated beforehand, and thus theprocessing time for the subsequent plasma treatment can also beshortened.

In the aforementioned process that imparts ink affinity, a plasmatreatment (O₂ plasma treatment) is performed in which oxygen in theatmospheric air is used as the reactive gas. Specifically, the substrate10 including the bank members 12 is placed onto a test stage within theinterior of a heater, and oxygen in a plasma state is irradiatedthereon.

This O₂ plasma treatment may be performed under the conditions of aplasma power of 100 to 800 kW, an oxygen gas flow of 50 to 100 cc/min, asubstrate transport speed of 0.5 to 10 mm/sec, and a substratetemperature of 70 to 90° C. Furthermore, the heating performed accordingto this test stage is conducted mainly to maintain the temperature ofthe pre-heated substrate 10.

By utilizing this O₂ plasma treatment, hydroxyl groups are introduced inthe exposed surfaces of the transparent electrode 11 and inorganicsubstance bank layer 12 a, and on the entire surface of the organicsubstance bank layer 12 b, thereby imparting the aforementioned with inkaffinity properties.

Subsequently, in the aforementioned process that imparts ink repellentproperties, a plasma treatment (CF₄ plasma treatment) is performed inthe atmospheric air wherein tetrafluoromethane (tetra-fluoro-carbon) isused as the reactive gas.

Specifically, the substrate 10 including the bank members 12 is placedonto a test stage within the interior of a heater, andtetrafluoromethane in a plasma state is irradiated thereon.

This CF₄ plasma treatment may be performed under the conditions of aplasma power of 100 to 800 kW, a tetrafluoromethane gas flow of 50 to100 cc/min, a substrate transport speed of 0.5 to 10 mm/sec, and asubstrate temperature of 70 to 90° C. Furthermore, the heating performedaccording to this test stage is conducted mainly to maintain thetemperature of the pre-heated substrate 10, in the same manner as withthe first plasma treatment chamber 52.

Furthermore, the reactive gas is not limited to only tetrafluoromethane,but other fluorocarbon gases may also be used.

According to this CF₄ plasma treatment, ink repellent properties areimparted by introducing fluorine groups into the organic substance banklayer, which displays an ink affinity by means of the previous process.Hydroxyl groups of the organic substances such as acrylic resin andpolyimide resin forming the aforementioned organic substance bank layer12 b are substituted easily by the fluorine groups by irradiating afluorocarbon in a plasma state so that they are imparted with theaforementioned ink repellent properties.

On the other hand, the exposed surfaces of the transparent electrode 11and inorganic bank layer 12 a are slightly affected by this CF₄ plasmatreatment. However, the CF₄ plasma treatment does not have an affect onthe affinity.

By cooling the substrate 10, which has been heated for the plasmatreatment back, to room temperature or to a predetermined temperature (atemperature to execute the ink jet process) in the subsequent coolingprocess, it is possible to execute formation of the holeinjection/transport layer at a constant temperature. As a result, it ispossible to continuously discharge the ink droplets at a constantvolume, at the time of discharging the composition ink containing thehole injection/transport layer material according to an ink jet method.In this manner, a uniform hole injection/transport layer can be formed.

According to the aforementioned plasma treatment process, bysequentially performing the aforementioned O₂ plasma treatment and CF₄plasma treatment with respect to the organic substance bank layer 12 aand inorganic bank layer 12 b, including different materials, it ispossible to easily provide both a region of ink affinity and an inkrepellent region in bank member 12.

Subsequently, in the hole injection/transport layer formation process, ahole injection/transport layer 16 is formed by discharging an inkcomposition 15 containing the hole injection/transport layer materialfrom an opening 13 above the aforementioned transparent electrode 11,and then drying and heat treating the aforementioned.

Furthermore, after forming the aforementioned hole injection/transportlayer, it is preferable to perform processes in an inert gasenvironment, such as that of a nitrogen atmosphere and/or argonatmosphere without water and oxygen.

As shown in FIG. 2, an ink composition 15 containing the holeinjection/transport layer material is first filled into an ink jet head14, the discharge nozzle of which faces an opening 13. While mutuallymoving this inkjet head 14 and the substrate 10, the ink composition 15,the liquid amount per droplet of which is controlled, is then dischargedonto the transparent electrode 11 from the aforementioned ink jet head14.

A mixture of a polythiophene derivative, such as polyethylenedioxythiophene (PEDOT) or the like, and a polystyrene sulfonate (PSS),which has been dissolved in a polar solvent, may be used as the inkcomposition 15, for example. The aforementioned polar solvent mayinclude, for example, isopropyl alcohol (IPA), normal butanol,γ-butyrolactone, N-methyl pyrolidone (NMP), 1,3-dimethyl-2-imidazolidone(DMI), derivatives thereof, and glycol ethers such as carbitol acetate,butylcarbitol acetate, and the like.

More concrete examples of the ink composition 15 may include acomposition including 11.08% by weight of a PEDOT/PSS mixture (whereinthe ratio of PEDOT to PSS is 1 to 20); 1.44% by weight of PSS; 10% byweight of IPA; 27.48% by weight of NMP; and 50% by weight of DMI.Furthermore, the viscosity of the ink composition is preferably 2 to 20Ps, and more preferably approximately 7 to 10 cPs.

By using the aforementioned ink composition, it is possible to performstable discharge of the ink composition from a discharge nozzle withoutplugging of the discharge nozzle of the ink jet head 14.

Moreover, with regard to the material including the holeinjection/transport layer 16, the same material may be used for eachlight emitting layer of R, G and B. Alternatively, these materials mayalso differ from each other as well.

The discharged ink composition 15 then spreads onto the transparentelectrode 11 and the inorganic bank layer 12 a of the opening 13, bothof which have been imparted with ink affinity properties. In addition,even if the ink composition 15 falls out of the predetermined dischargeposition, and is discharged onto the organic substance bank layer 12 b,this ink composition 15 falls away from the organic substance bank layer12 b and flows into an opening 13 without wetting the organic substancebank layer 12 b.

The discharge amount of the ink composition 15 may be determinedaccording to the size of the opening 13, thickness of the holeinjection/transport layer, concentration of the hole injection/transportlayer in the ink composition 15, and the like.

In addition, the discharge of the ink composition 15 to the opening 13may be divided over several cycles instead of discharging all at once.In such a case, the discharge amount of the ink composition 15 may beidentical each time, or alternatively may vary with each cycle.Furthermore, the ink composition is not necessarily discharged onto thesame location within opening portions 13 every time, and the inkcomposition 15 may be discharged to different locations within openingportion 13.

Subsequently, a hole injection/transport layer 16 is formed, as shown inFIG. 3, by drying the discharged ink composition 15, and evaporating thepolar solvent contained in the ink composition 15.

The drying process, for example, may be performed at room temperatureunder a pressure of approximately 133.3 Pa (1 Torr) in nitrogenatmosphere. A pressure that is excessively low leads to clumping of theink composition 15, and hence is not desirable. Furthermore, a smallamount of the ink composition 15 remains on and adheres to thesurrounding wall surface of the bank member 12. Thus, if theaforementioned drying temperature exceeds room temperature, theevaporation speed of the polar solvent is increased, which leads to anexcessive amount of the ink composition 15 remaining on theaforementioned wall surface. Accordingly, the aforementioned dryingprocess is preferably performed at a temperature not to exceed roomtemperature.

After the drying process, the polar solvent and water remaining in thehole injection/transport layer 16 are preferably removed by heattreating the aforementioned for approximately 10 minutes at 200° C. innitrogen, or preferably in vacuum.

In the aforementioned hole injection/transport layer formation process,the discharged ink composition 15 blends into the exposed surfaceportions of the transparent electrode 11 and inorganic bank layer 12 a,which exhibit ink affinity properties, while for the most part notadhering to the ink repellent, organic substance bank layer 12 b.Therefore, even in the case when the ink composition 15 is mistakenlydischarged onto the aforementioned organic substance bank layer 12 b,this ink composition 15 falls away and flows onto the exposed surfaceportions of the transparent electrode 11 and inorganic bank layer 12 a,both of which exhibits ink affinity properties. As a result, a holeinjection/transport layer 16 can be reliably formed onto theaforementioned transparent electrode 11.

Subsequently, a surface reforming process is performed prior toconducting the light emitting layer forming process. In other words, inorder to prevent the hole injection/transport layer 16 from beingre-dissolved while forming the light emitting layer, a non-polar andinsoluble solvent to the hole injection/transport layer 16 is used withrespect to the hole injection/transport layer 16, as the solvent for theink composition at the time of forming the light emitting layer.

However, on the other hand, the aforementioned hole injection/transportlayer 16 has a low affinity with the aforementioned non-polar solvent.Thus, even when the ink composition of the light emitting layercomprising the non-polar solvent is discharged onto the aforementionedhole injection/transport layer 16, the ink composition may be repelledby the hole injection/transport layer 16, which makes it impossible toadhere the light emitting layer with the hole injection/transport layer16, or alternatively makes it impossible to form uniform coating of thelight emitting layer.

Hence, in order to increase the surface affinity of the aforementionedhole injection/transport layer 16 with the aforementioned non-polarsolvent, it is preferable to perform a surface reforming process priorto the formation of the light emitting layer.

In this surface reforming process, a solvent for use in surfacereforming, which is identical or similar to the non-polar solvent of theink composition used at the time of forming the light emitting layer, iscoated onto the aforementioned hole injection/transport layer 16 by anink jet method, spin coating method, or dip method, and dried thereon.

According to an ink jet method, the aforementioned coating is performedby filling a solvent for use in surface reforming into an ink jet head,and then discharging this surface reforming solvent onto the holeinjection/transport layer 16, while moving this ink jet head and thesubstrate 10 to each other, with the discharge nozzle of the ink jethead facing the aforementioned hole injection/transport layer 16.

In addition, according to a spin coat method, a substrate 10 is, forexample, loaded onto a stage, and a surface reforming solvent is addedthereto in a dropwise manner from above. Subsequently, the substrate 10is rotated to spread the surface reforming solvent over the entire holeinjection/transport layer 16 on the substrate 10. Furthermore, althoughthe surface reforming solvent is temporarily spread over the inkrepellent organic substance bank layer 12 b, this surface reformingsolvent is blown aside by the centrifugal force of the aforementionedrotation, and hence ends up coating only the aforementioned holeinjection/transport layer 16.

Furthermore, the coating according to a dip method involves immersing asubstrate 10 in a surface reforming solvent, and following removal,spreading this surface reforming solvent over the entire holeinjection/transport layer 16. In this case as well, the surfacereforming solvent is temporarily spread over the ink repellent organicsubstance bank layer 12 b, but falls away from the ink repellent organicsubstance bank layer 12 b and removed from the surface reformingsolvent. As a result, the surface reforming solvent ends up coating onlythe aforementioned hole injection/transport layer 16.

The surface reforming solvent used here may include compounds identicalto the non-polar solvent of the ink composition, such ascyclohexylbenzene, dihydrobenzofuran, trimethylbenzene,tetramethylbenzene, and the surface reforming solvent such as toluene,xylene, and the like are preferable for the spin coat method and thedipping method.

In particular, when performing the aforementioned coating according toan ink jet method, dihydrobenzofuran, trimethylbenzene,tetramethylbenzene, cyclohexylenzene, a mixture of these compounds,especially the same solvent mixture used in the ink composition and thelike are preferably used. In the case when performing the aforementionedcoating according to a spin coating or dip method, toluene, xylene, andthe like are preferably used.

With regard to the drying process, in the case when the coating has beenperformed according to an ink jet method, it is preferable to performthe aforementioned drying by loading the substrate 10 onto a hot plateand heating the aforementioned to a temperature of no greater than 200°C. in order to dry the surface reforming solvent. On the other hand, inthe case when the coating has been performed according to a spin coatingor dip method, the surface reforming solvent is preferably dried byeither blowing nitrogen onto the substrate 10, or by generating an airflow onto the surface of the substrate 10 by rotating the aforementionedsubstrate.

Moreover, it is also possible to perform the coating of the surfacereforming solvent after the drying process of the aforementioned holeinjection/transport layer formation process, and then conduct the heattreating process of the hole injection/transport layer formation processafter drying the coated surface reforming solvent.

By virtue of performing the aforementioned surface reforming process,the surface of the hole injection/transport layer 16 blends in easierwith the non-polar solvent. In addition, by virtue of the subsequentprocesses, it is possible to uniformly coat the ink compositioncontaining the light emitting layer material onto the aforementionedhole injection/transport layer 16.

Moreover, it is also possible to form an ultra thin hole transport layeronto the aforementioned hole injection/transport layer by forming an inkcomposition by dissolving a commonly used hole transport layer material,such as arylamine-type compound and the like, in the aforementionedsurface reforming solvent. The resultant ink composition is then coatedonto the hole injection/transport layer according to an ink jet method,and dried thereon.

Although the majority of this hole transport layer is dissolved into thelight emitting layer coated in a subsequent process, a small amountremains as a thin layer between the hole injection/transport layer 16and the light emitting layer. As a result, the energy barrier betweenthe hole injection/transport layer 16 and the light emitting layer isreduced, which in turn allows for easy movement of the hole andenhancement of light emitting efficiency.

In the subsequent light emitting layer formation process, the inkcompositions 17 a, 17 b and 17 c (not shown), each including a solutecomponent, e.g., an organic electro-luminescent material or the like,and a solvent, are discharged according to the following sequence onto ahole injection/transport layer 16 which has undergone surfacereformation. Drying and heat treatment of the aforementioned are thenperformed to sequentially form the light emitting layers 18 a, 18 b and18 c.

The aforementioned organic electro-luminescent material may includefluorene-type high molecular weight derivatives such as shown inchemical formula 1 to chemical formula 5, shown below.

Examples of the organic electro-luminescent materials include(poly)-paraphenylene-vinylene derivatives, polyphenylene derivatives,polyfluorene derivatives, polyvinyl carbazol, polythiophene derivatives,perylene-type pigments, coumarin-type pigments, rhodamine-type pigments,as well as low molecular weight organic EL materials and large molecularweight EL materials that are soluble in other benzene derivatives. Forexample, it is possible use rublene, perylene, 9,10-diphenyl anthracene,tetraphenyl butadiene, Nile Red, coumarin 6, quinacridone, and the like.

Furthermore, in the chemical formula 1 to the chemical formula 5, nrepresents the degree of polymerization. In the chemical formula 1, n isin a range of 1,000 to 500,000, in the chemical formula 2, n is in arange of 1,000 to 500,000, in the chemical formula 3, n is in a range of1,000 to 500,000; in the chemical formula 4, n ranges 1,000 to 500,000,and in the chemical formula 5, n ranges 1,000 to 500, 00. In addition,in the chemical formula 5, R represents H, CH₃, C₂H₅ and so on.

As the non-polar solvent, it is preferable to use a compound that isinsoluble in the hole injection/transport layer 16, for example,cyclohexylbenzene, dihydrobenzofuran, trimethylbenzene,tetramethylbenzene, and the like.

By employing the non-polar solvent in the ink composition of the lightemitting layer, it is possible to coat the ink composition withoutre-dissolving the hole injection/transport layer 16.

Furthermore, as the solute component, beside the organicelectro-luminescent material, it is also possible to include anappropriate amount of a binder, such as a surface active agent, athickener and the like.

As shown in FIG. 4, an ink composition 17 a is discharged onto a holeinjection/transport layer 16 by filling the ink composition 17 a into anink jet head 14 and then discharging this ink composition, the liquidamount per droplet of which is controlled, from a discharge nozzle whilemoving both this ink jet head 14 and substrate 10 with respect to eachother, with the discharge nozzle of the ink jet head 14 facing theaforementioned hole injection/transport layer 16.

In this case, the discharged ink composition 17 a spreads out and blendsinto the hole injection/transport layer 16, without for the most partadhering to the organic substance bank layer 12 b, which has previouslyundergone an ink repellent treatment. As a result, even when this inkcomposition 17 a is mistakenly discharged onto the organic substancebank layer 12 b, it falls away and flows onto the holeinjection/transport layer 16. In this manner, it is possible to form alayer of the ink composition 17 a which is tightly adherent to the holeinjection/transport layer 16.

The amount of the ink composition 17 a is determined based on thethickness of the light emitting layer 18 a to be formed, theconcentration of the light emitting layer material within the inkcomposition, and the like.

In addition, the discharge of the ink composition 17 a onto the holeinjection/transport layer 16 may be performed with the dropwise additionof the ink composition 17 a divided over several cycles instead ofdischarging all at once. In such a case, the droplet amount of the inkcomposition 17 a may be identical each time, or alternatively may varywith each cycle. Furthermore, instead of being discharged to the samelocation on the hole injection/transport layer 16 each time, the inkcomposition 17 a droplets may also be discharged arranging differentlocations within the hole injection/transport layer 16.

Subsequently, a light emitting layer 18 a is formed, as shown in FIG. 5,by drying the discharged ink composition 17 a, and evaporating the polarsolvent contained in the ink composition 17 a.

The drying process, for example, may be performed at room temperatureunder a pressure of approximately 133.3 Pa (1 Torr) in nitrogenatmosphere for 5-10 minutes, or by spraying nitrogen thereon at 40° C.for 5-10 minutes.

Other methods for performing the aforementioned drying may include, forexample, a far infrared irradiation method, a high-temperature nitrogengas spraying method, and the like.

Subsequently, as shown in FIG. 6, a second light emitting layer 18 b(FIG. 7) is formed by dropwise addition and drying of an ink composition17 b, in the same manner as with the aforementioned ink composition 17a. Thereafter, a third light emitting layer 18 c is formed in a similarmanner by dropwise addition and drying of an ink composition 17 c, asshown in FIG. 7, to yield a substrate having three types of lightemitting layers 18 a, 18 b, and 18 c formed thereon.

Here, the formation sequence of the aforementioned three types of lightemitting layers 18 a, 18 b, and 18 c is determined in the followingmanner.

First, in the case when the number of organic electro-luminescentmaterials is different, the formation sequence starts with the layerincluding the fewest organic electro-luminescent materials. If a lightemitting layer including a color having a large number of components isformed first, phase separation may occur due to re-dissolution of theinitially formed light emitting layer, by the solvent vapor evaporatedfrom the ink composition of a light emitting layer including a differentcolor, which has been formed later.

In addition, in the case when the number of organic electro-luminescentmaterials including the respective ink compositions is identical, theaforementioned formation sequence starts with the ink compositionincluding the organic electro-luminescent materials that are mostdifficult to phase separate. The degree of difficulty for phaseseparation may be determined by drying the ink compositions to becompared under identical drying conditions, and comparing the degree ofphase separation of the resultant light emitting layers. At this time,the aforementioned “identical” drying conditions may include naturalretention, drying by heating, and drying under reduced pressure, and thenatural retention is preferably selected.

The degree of phase separation may be determined by the amount of lightof a wavelength obtained at the time of complete phase separation thatremains in the light emitting spectrum of the resultant light emittinglayer. In addition, it is also possible to determine the degree of phaseseparation by the proportion of light of a wavelength resulting whencomplete phase separation does not occur, in the light emitting spectrumof the resultant light emitting layer.

In the cathode formation process, a cathode 19 is formed over the entiresurfaces of the light emitting layers 18 a, 18 b, 18 c, and organicsubstance bank layer 12 b. This cathode 19 may be formed by laminating aplurality of materials.

For example, it is preferable to use a material such as Ca and Ba, whosework function is low, to form a layer close to the light emitting layer,and sometimes it is more preferable to form a thin LiF layer as anunderlayer, depending on the nature of the layer material formed on thelight emitting layer. In addition, the cathode upper layer (sealingside) is preferably formed by materials such as an Al layer, an Aglayer, a Mg/Ag layer and the like, which have a larger work functionthan that of the lower layer. The thickness of the upper cathode layeris preferably within a range of 100 to 1,000 nm, and more preferably,within a range of 200 to 500 nm.

The aforementioned cathode layer is preferably formed by, for example,an evaporation method, spattering method, CVD method or the like. Inparticular, formation according to an evaporation method is preferablefrom the point of view of preventing the light emitting layers 18 a, 18b and 18 c from being damaged by heat.

In addition, it is also possible to form the lithium fluoride layer ononly the light emitting layers 18 a, 18 b and 18 c, or alternativelyonly on a specified light emitting layer. In such as case, the cathodeupper layer formed from calcium contacts the other light emittinglayers.

In addition, it is also possible to provide a protective layercomprising SiO, SiO₂, SiN, or the like onto the cathode layer to preventfrom oxidation.

Lastly, in the sealing process, a sealing layer 20 is formed by coatinga sealing agent including a thermosetting resin or ultraviolet lightcured resin onto the entire surface of the cathode 19. Furthermore, asubstrate used to seal (not shown in the figures), is then laminatedonto the sealing layer 20.

This sealing process is preferably conducted in the environment of aninactive gas, such as nitrogen, argon, helium, or the like. In the casewhen performing the aforementioned sealing process in air and a defect,such as pin hole or the like, is generated in the cathode layer, water,oxygen, and the like may penetrate into the cathode 19 through theaforementioned defect, resulting in the undesirable oxidation of thecathode 19.

In this manner, an organic electro-luminescent device shown in FIG. 8 isobtained.

According to the present embodiment, the discharge formation of a layerof the ink composition including a greater number of organic materialsis performed after that of the ink composition including fewer organicelectro-luminescent materials. In addition, in the case when the inkcompositions include the same number of organic electro-luminescentmaterials, this discharge formation of a layer is performed in adischarge sequence, starting with the ink composition include theorganic electro-luminescent materials that are most difficult to phaseseparate. As a result, it is possible to prevent the phase separationoccurring due to re-dissolution after the discharge formation of alayer. Accordingly, an organic electro-luminescent device havingsuperior display properties can be reliably manufactured.

In the following, the electronic equipment including the organicelectro-luminescent device manufactured according to the aforementionedembodiment will be described using concrete examples.

FIG. 10A is a perspective view showing an example of a portabletelephone. In FIG. 10A, reference numeral 600 denotes a main body 600 ofthe portable telephone, and 601 denotes a display unit 601 including anorganic electro-luminescent device.

FIG. 10B is a perspective view showing an example of a portableinformation processing apparatus, e.g., word processor, personalcomputer, or the like. FIG. 10B shows an information processingapparatus 700, an input unit 701, such as a keyboard or the like, themain body 703 of the information processing apparatus, and an organicelectro-luminescent device as a display unit 702.

FIG. 10C is a perspective view showing an example of an electronicwristwatch. In FIG. 10C, the main body 800 of the watch, and an organicelectro-luminescent device as a display unit 801 are shown.

According to the present embodiment, it is possible to provideelectronic equipment that is equipped with a display apparatuspossessing superior display properties.

EXAMPLES

The organic electro-luminescent devices of the Examples and ComparativeExamples were manufactured according to the above-described embodiments.The concrete manufacturing conditions are described below. Theconditions are common to all of the Examples and Comparative Exampleexcept the formation sequence for manufacturing the light emittinglayer.

Bank Formation Process

A bank layer was formed so as to be opened on the transparent pixelelectrode made of ITO. Since the transparent electrode was formed in amatrix form having a pitch of 70.5 micron meter, the bank layer was alsoformed in a matrix form having a pitch of 70.5 micron meter. The banklayer (bank) was formed by laminating inorganic bank layers made of SiO₂and organic substance bank layers made of polyimide. Each layer wasformed on the etched layer formed by photolithographic technique.Circular openings were made for the bank layers and the opening for theorganic substance bank layer was formed in a diameter of 28 micron meterand the opening for the inorganic bank layer was formed in a diameter of44 micron meter. The organic substance bank layer was formed at a heightof 2 micron meter and the inorganic bank layer was formed at a height of150 nm.

Plasma Treatment Process

An O₂ plasma treatment was performed as a process for imparting inkaffinity. This O₂ plasma treatment was conducted under the conditions ofroomtemperature, atmospheric pressure, a power of 300 W, anelectrode-substrate distance of 1 mm, an oxygen gas flow amount of 100cc/min, a helium gas flow amount of 10 l/min, and a table transfer rateof 10 mm/s. Subsequently, a CF₄ plasma treatment was performed as aprocess for imparting ink repellent properties. This CF₄ plasmatreatment was conducted under the conditions of a CF₄ gas flow amount of100 cc/min, a helium gas flow amount of 10/min, and a table transferrate of 3 mm/s.

Hole Injection/Transport Layer Formation Process

An ink composition (a mixture of “Baytron P” manufactured by Bayer AGand a polystyrene sulfonate) for use in a hole injection/transport layershown in Table 1 was discharged from the head of an ink jet printer(MJ-9300 manufactured by Epson) at 15 pl to form a pattern coat. Thesolvent was then removed at room temperature under a vacuum (1 Torr) for20 minutes. The same ink composition for use in a holeinjection/transport layer was then discharged at 15 pl to form a patterncoat. After removing the solvent at room temperature under a vacuum (1Torr) for 20 minutes, a heat treatment was performed in air atmosphereat 200° C. (on a hot plate) for 10 minutes to form a holeinjection/transport layer.

TABLE 1 Ink Composition for Hole Injection/Transport Layer CompositionComposition Material name (wt %) hole injection/transport layer Bytron P11.08 materials Polystyrene sulfonate 1.44 Polar solvents Isopropylalcohol 10 N-methyl pyrolidone 27.48 1,3-dimethyl-2- 50 imidazolidoneSurface Reforming Process

1,2,3,4-tetramethyl benzene was discharged from an ink jet printer(MJ-930C manufactured by Epson) to form a coat. Subsequently, theaforementioned was placed on a hot plate that was heated to atemperature below 200° C. and dried.

Light emitting layer Formation Process

The ink compositions shown in Tables 2 to 4 were prepared. Table 2 showsan ink composition (green) for a light emitting layer, Table 3 shows anink composition (blue) for a light emitting layer; and Table 4 shows anink composition (red) for a light emitting layer. Furthermore, compounds1, 2, 4, and 5 in the Tables are respectively described above inChemical Formula 1 to 5.

TABLE 2 Ink Composition (Green) for a Light emitting layer CompositionComposition Material name weight Light emitting layer Compound 1 0.76 gMaterials Compound 2 0.20 g Compound 4 0.04 g Solvent1,2,3,4-tetramethyl benzene 100 ml

TABLE 3 Ink Composition (Blue) for a Light emitting layer CompositionComposition Material name weight Light emitting layer Compound 1 1.00 gMaterial Solvent 1,2,3,4-tetramethyl benzene 100 ml

TABLE 4 Ink Composition (Red) for a Light emitting layer CompositionComposition Material name weight Light emitting layer Compound 1 0.7 gMaterials Compound 2 0.2 g Compound 5 0.1 g Solvent 1,2,3,4-tetramethylbenzene 100 ml

EXAMPLE 1

Initially, a blue light emitting layer was prepared by discharging theink composition (blue) for a light emitting layer comprising aconcentration of 1% (wt/vol) shown in Table 3, from an ink jet printer(MJ-930C manufactured by Epson) by 20 pl under an N₂ gas flow, and thendrying under the conditions of 25° C. and 1 atm.

Subsequently, a green light emitting layer was prepared by dischargingthe ink composition (green) for a light emitting layer including aconcentration of 1% (wt/vol) shown in Table 2, into a neighboringopening 13 at 20 pl under an N₂ gas flow, and then drying under theconditions of 25° C. and 1 atm.

EXAMPLE 2

Initially, a blue light emitting layer was prepared by discharging theink composition (blue) for a light emitting layer including aconcentration of 1% (wt/vol) shown in Table 3, from an ink jet printer(MJ-930C manufactured by Epson) at 20 pl under an N₂ gas flow, and thendrying under the conditions of 25° C. and 1 atm.

Subsequently, a red light emitting layer was prepared by discharging theink composition (red) for a light emitting layer including aconcentration of 1% (wt/vol) shown in Table 4, into a neighboringopening 13 at 20 μl under an N₂ gas flow, and then drying under theconditions of 25° C. and 1 atm.

Thereafter, a green light emitting layer was prepared by discharging theink composition (green) for a light emitting layer including aconcentration of 1% (wt/vol) shown in Table 2, into a neighboringopening 13 at 20 pl under an N₂ gas flow, and then drying under theconditions of 25° C. and 1 atm.

COMPARATIVE EXAMPLE 1

Initially, a green light emitting layer was prepared by discharging theink composition (green) for a light emitting layer including aconcentration of 1% (wt/vol) shown in Table 2, from an ink jet printer(MJ-930C manufactured by Epson) at 20 pl under an N₂ gas flow, and thendrying under the conditions of 25° C. and 1 atm.

Subsequently, a blue light emitting layer was prepared by dischargingthe ink composition (blue) for a light emitting layer including aconcentration of 1% (wt/vol) shown in Table 3, into a neighboringopening 13 at 20 pl under an N₂ gas flow, and then drying under theconditions of 25° C. and 1 atm.

Cathode Formation Process

After forming a LiF layer having a thickness of 2 nm by a vapordeposition method as the cathode layer, a calcium layer having athickness of 20 nm was formed by a vapor deposition method. An aluminumlayer of 200 nm was then formed as the cathode layer by a spatteringmethod.

Sealing Process

A sealing layer was formed by coating a sealing agent including an epoxyresin onto the entire surface of the cathode. Furthermore, a substratefor use in sealing was laminated onto the aforementioned sealing layerto prepare the organic electro-luminescent device according to theExamples and Comparative Example.

Evaluation

The light emitting spectrums of the green light emitting layers of theorganic electro-luminescent device according to the Comparative Exampleand Example 1 are shown in FIGS. 9A and 9B. As shown in FIG. 9A, a blueluminescent (430 nm) originated from the compound 1 remained in thegreen light emitting layer of the Comparative Example showed a spottyluminescent exhibiting color of light blue.

In contrast, as shown in FIG. 9B, the green light emitting layer ofExample 1 displayed a green fluorescent luminescent (530 nm) having anapproximately uniform spectrum.

In addition, the blue light emitting layers of the Comparative Exampleand Example 1 both displayed a uniform spectrum of blue luminescent (430nm) originated by the compound 1.

Hence, the formation efficiency of forming the light emitting layers inthe order starting with the layers having the fewest number of organicelectro-luminescent materials was confirmed from the aforementioned.

In addition, the blue light emitting layer (430 nm), red light emittinglayer (640 nm), and green light emitting layer (530 nm) of the organicelectro-luminescent device according to Example 2 each showed a uniformspectrum.

Both the ink compositions of the (red) light emitting layer and (green)light emitting layer include three organic electro-luminescentmaterials, however, upon comparing the difficulty of phase separation ofthese ink compositions under the conditions of N₂ flow, the inkcomposition of the (red) light emitting layer was found to be moredifficult to phase separate.

Hence, in the case when the ink compositions include an identical numberof organic electro-luminescent materials, the efficiency of forming thelight emitting layers in the order starting with the layer that is themost difficult to phase separate was confirmed from the aforementioned.

As described above, according to the method for manufacturing an organicelectro-luminescent device of the present invention, it is possible tomanufacture an organic electro-luminescent device having superiordisplay properties in which phase separation due to re-dissolution aftercompletion of forming layer can be prevented.

In addition, the organic electro-luminescent device according to thepresent invention includes a uniform light emitting layer(s) and alsoexhibits superior display properties.

In addition, the present invention provides the electronic equipmentwhich is capable of having superior display properties.

1. A manufacturing method for an organic electro-luminescent device,comprising: forming light emitting layers by discharging, above asubstrate, at least two compositions, each including two or more organicelectro-luminescent material; and ordering discharging said compositionsabove the substrate starting with a composition which has a fewestnumber of organic electro-luminescent materials, wherein there is formeda layer in a state in which each of the organic electro-luminescentmaterials is uniformly mixed without separation.
 2. A manufacturingmethod for an organic electro-luminescent device, comprising: forminglight emitting layers by discharging, above a substrate, at least twocompositions, each including two or more organic electro-luminescentmaterial; and when discharging compositions which has a same number oforganic electro-luminescent materials, ordering discharging saidcompositions above the substrate starting with a composition which ismost difficult to be phase separated after the layer is formed, whereinthere is formed a layer in a state in which each of the organicelectro-luminescent materials is uniformly mixed without separation. 3.The manufacturing method for an organic electro-luminescent deviceaccording to claim 1, further including the step of, during twocontinuous cycles of discharging said compositions, performing thesubsequent discharging of a composition after the composition dischargedin a first cycle are dried.
 4. The manufacturing method for an organicelectro-luminescent device according to claim 3, further including thesteps of, prior to said step for forming a light emitting layer, formingpixel electrodes corresponding to a plurality of pixel regions and banksseparating said pixel regions above said substrate; forming a holeinjection/transport layer above said pixel electrodes of said pluralityof pixel regions; and after said process for forming a light emittinglayer, forming a counter electrode above said light emitting layer. 5.The manufacturing method for an organic electro-luminescent deviceaccording to claim 2, further including the step of, during twocontinuous cycles of discharging said compositions, performing thesubsequent discharging of a composition after the composition dischargedin a first cycle are dried.
 6. The manufacturing method for an organicelectro-luminescent device according to claim 5, further including thesteps of, prior to said step for forming a light emitting layer, formingpixel electrodes corresponding to a plurality of pixel regions and banksseparating said pixel regions above said substrate; forming a holeinjection/transport layer above said pixel electrodes of said pluralityof pixel regions; and after said process for forming a light emittinglayer, forming a counter electrode above said light emitting layer.